Your sense of scale is lacking. A corporation with billions of dollars, thousands of employees, and politicians beholden to it offers you a wage to work for it. Your bargaining power is that you might go work elsewhere. If most of the "elsewheres" for your particular skills are similar corporations, and if they have colluded and agreed not to offer you a job just if you already are working at any of them, then once you have that first job, you are no longer free to bargain. You, as a single individual, have been decisively ganged up on.
A labor union, as a response to such power (and labor unions historically very much were formed as response to such power) is also a way of ganging up. Labor unions have never been as rich as the corporations, and have rarely had equivalent political sway. But to negotiate as anything like an equal with a gang - here not just a single large corporation but a gang of large corporations - you need a gang behind you too. This is an excellent reason to unionize tech workers.
Having corporations and government melded into one isn't capitalism, by the way. It's the classic Italian definition of fascism. That some libertarians want to have that mix with government being the relatively weaker partner and corporations stronger does not change the satisfaction of the definition. It's the melding that is fascism, not the relative distribution of power within the meld.
In a true democracy corporations are kept separate to compete with each other, and government is often oppositional to their interests. Workers are allowed to form unions as a counter to corporate power. This creates, paradoxically, stronger corporations, since they are no longer coddled by government and allowed to suppress wages, they have to actually be clever and productive to profit. Fascism isn't just a nasty name; it's an inferior system ultimately, even from the corporate point of view.